1. Field of the Invention
The present invention relates to a positive resist composition, especially to a chemically amplified positive resist composition, suitable as a micropatterning material, especially for the VLSI manufacture, or photomask patterning, which has a high alkaline dissolution-rate contrast before and after exposure, high sensitivity, high resolution, reduced line edge roughness, and an improved etch resistance on exposure to a high energy beam.
2. Description of the Related Art
In recent years, the higher the circuit density and speed of LSI becomes, the finer a pattern rule becomes rapidly. Increasing the NA of the lens system, improved performance of resist and shift to shorter wavelength results in quick shift to finer patterning. Especially shift to shorter wavelength from I-line radiation (365 nm) to KrF (248 nm) causes a big change, and it comes to mass-produce a device under 0.18 μm rule. The chemically amplified positive resist composition wherein an acid is used as a catalyst (for example, see Japanese Patent Publication No. 2-27660 and Japanese Patent Application Laid-open (KOKAI) No. 63-27829) has an outstanding feature to achieve higher resolution and sensitivity of resist, and thus has become a main resist composition especially for deep-ultraviolet lithography.
The resist composition for KrF excimer lasers has began to be used generally for a 0.3-micron process, and it has also been began to be applied to mass-production under 0.18-micron rule via a 0.25-micron rule. Furthermore, study of a 0.15 micron rule has also been started, and the shift to finer patterning is accelerated increasingly. It is expected that a design rule should be 0.13 μm or less according to a shift to shorter wavelength from KrF excimer lasers to ArF excimer lasers (193 nm). However, it was hard to use novolac and polyvinyl phenol resin which have been used conventionally as a base resin for resist, since it has a quite strong absorption near the wavelength of 193 nm. Then, aliphatic resins such as acrylic resins or cycloolefin resins have been examined to ensure transparency and a desired dry etching resistance (for example, see Japanese Patent Application Laid-open (KOKAI) No. 9-73173, Japanese Patent Application Laid-open (KOKAI) No. 10-10739, Japanese Patent Application Laid-open (KOKAI) No. 9-230595 and International publication No. 97/33198).
Among them, the resist comprising (meth)acrylic based resin with a high resolution has been examined. As (meth)acrylic resin, the combination of the (meth)acrylic derivative which has methyl adamantane ester as an acid labile unit and the (meth)acrylic derivative which has an ester of a lactone ring as an adhesion group has been proposed (for example, see Japanese Patent Application Laid-open (KOKAI) No. 9-90637). Furthermore, norbornyl lactone has been proposed as an adhesion group wherein an etch resistance is enhanced (for example, see Japanese Patent Application Laid-open (KOKAI) No. 2000-26446 and Japanese Patent Application Laid-open (KOKAI) No. 2000-159758).
Reduction of line edge roughness and reduction of residue after development are mentioned as one of the tasks in ArF lithography. Swelling at the time of development is mentioned as one of the causes for line edge roughness. Although polyhydroxy styrene used as a resist for KrF lithography doesn't swell easily since phenol moiety is a weak acidic group and has a moderate aqueous alkaline solubility, the polymer comprising a highly hydrophobic alicyclic group swells easily since it is dissolved with a carboxylic acid with high acidity.
Here, the amount of swelling during development has been reported by measurement of the development characteristics of the resist according to the QCM (Quartz Crystal Microbalance) method (for example, see Proc. SPIE Vol. 3999 p 2 (2000)). Although swelling of the film during development cannot be observed by a conventional optical interference thickness-measurement method, it is possible to observe increase in weight of the film by swelling according to the QCM method, since the weight change of a film is measured electrically. In the non-patenting reference 1, swelling of the ArF resist based on cycloolefin polymer is disclosed. Significant swelling is observed especially in the case that a carboxylic acid is used as an adhesion group.
The present invention has been made in order to solve such problems. The object of the present invention is to provide a positive resist composition having high sensitivity and high resolution on exposure to a high energy beam, wherein line edge roughness is reduced since swelling at the time of development is suppressed, and the amount of the residue after development is small.